1. Field of Invention
The present invention relates to an electric optical apparatus employing a Silicon-On-Insulator (hereinafter SOI) technique and a manufacturing method thereof, a projection display, and an electronic instrument. More specifically, the invention relates to a highly reliable electric optical apparatus capable of being manufactured with high yield and a manufacturing method thereof, and a highly reliable projection display and electronic instrument including the electric optical apparatuses.
2. Description of Related Art
The SOI technique, in which a semiconductor thin film made of silicon, etc., is formed on an insulating substrate so as to form a semiconductor device therefrom. Such a semiconductor device provides advantages in that elements can be increased in speed, r electric power consumption can be reduced, and it can be highly integrated so as to be preferably incorporated into the electric optical apparatus, for example.
In order to manufacture the electric optical apparatus employing the SOI technique, a semiconductor substrate having a monocrystalline semiconductor layer made of monocrystalline silicon, etc., is bonded on a supporting substrate so as to form a thin-film monocrystalline semiconductor layer by polishing or the like, so that the thin-film monocrystalline semiconductor layer is formed to be a transistor element, such as a thin-film transistor (hereinafter TFT), to drive liquid crystal.
Also, the electric optical apparatus employing the SOI technique has been applied in the related art to a liquid-crystal light valve of a projection display, such as a liquid crystal projector. In such a liquid-crystal light valve, when the supporting substrate has optical transparency, incident light from a display surface is reflected at an interface of the supporting substrate in the back side, so that it may enter a channel region of the transistor element, such as the TFT, as returned light. Therefore, a liquid-crystal light valve is put forward, in which a light-shielding layer formed at a position corresponding to the transistor-element channel region in the front side of the supporting substrate to shield the returned light.
Also, in such a liquid-crystal light valve having the light-shielding layer formed in the front side of the supporting substrate, an electric potential of the light-shielding layer is fixed at a constant potential by electrically connecting the light-shielding layer to a potentiostatic source, so that changes in the electric potential of the light-shielding layer do not have an adverse affect on the transistor element.
In order to manufacture such an electric optical apparatus having the light-shielding layer formed on the front surface of the supporting substrate, after the light-shielding layer is patterned on the front surface of the supporting substrate and covered with an insulating layer thereon so as to be flattened by polishing, the obtained flattened surface is bonded to a semiconductor substrate. Then, by polishing a monocrystalline semiconductor layer constituting the semiconductor substrate, a thin-film monocrystalline semiconductor layer is formed to have the transistor element such as the TFT for driving liquid crystal. A contact hole, which passes through the insulating layer formed on the supporting substrate to the light-shielding layer, is formed by wet etching at a position where the thin-film monocrystalline semiconductor layer of the semiconductor substrate bonded on the supporting substrate does not exist, so that the light-shielding layer and the potentiostatic source are electrically connected via the contact hole.